In the electronic material industry, phosphorus-containing resins or flame retardants are usually applied to achieve bromine-free flame retardancy, and combined with nitrogen-containing resins or flame retardants to achieve synergistic phosphorous-nitrogen flame retardancy. Nitrogen element in benzoxazine resin, combined with phosphorus element, can achieve the V-0 level of UL 94 via a lower phosphorus content. In combination with a low curing shrinkage and a better moisture and heat resistance, it is widely used. Due to the structural feature of benzoxazine resin, the ring-opening polymerization of benzoxazine needs a higher temperature, which brings about difficulties to the industrialized mass production and becomes an application difficulty.
Many studies have been made on the aforesaid difficulty by research fellows in the industry, and their work is primarily concentrated on the effects of amine curing agents, phenolic resins, organic acids and the like on the reaction of benzoxazine and the mechanism discussion. For the industry of printed circuit boards (copper clad laminates), it is difficult to convert and apply these research results. The reasons lie in that amine curing agents have a worse heat resistance, and the semi-finished products have a short storage period; although phenolic resins have a better heat resistance, it has worse dielectric properties and a lower peeling strength; organic acids have an obvious ring-opening effect on benzoxazine, however, due to the oven temperature of up to more than 200° C., acids having a low boiling point will evaporate completely during the production of copper clad laminates, and cannot catalyze the ring-opening and polymerization of benzoxazine during lamination process; organic acids having a high boiling point will remain in the resin composition, which increases the risk of delamination and popcorn in PCB due to heat during the production. Thus there are always difficulties for the application of benzoxazine resins.